Traction motor drive system for a locomotive

ABSTRACT

A traction motor drive system includes a plurality of armatures arranged in parallel with each other and a plurality of field circuits arranged in series with one another. The plurality of field circuits is arranged in parallel with the armatures. The traction motor drive system also includes a field isolation system including a shunt circuit associated with at least one field circuit. The field isolation system includes a first field switch arranged in series with the plurality of field circuits and configured to switch between a first terminal of the shunt circuit and a first field terminal of at least one field circuit. The field isolation system includes a second field switch, arranged in series with the plurality of field circuits and configured to switch between a second terminal of the shunt circuit and a second field terminal of at least one field circuit.

TECHNICAL FIELD

The present disclosure relates generally to traction motor drive systemsand, more particularly, to systems and methods for isolating DC tractionmotor components on a locomotive.

BACKGROUND

Traction motors are commonly used in electrically powered rail vehiclessuch as diesel electric locomotives. Many locomotives today employ aplurality of DC traction motors, typically four or six, to providesufficient towing power for hauling large payloads over long distances.In some cases, motors are connected in series or parallel, so that theycan operate from a common electrical bus, simplifying wiring andelectric control of the motors.

In some traction motor systems, the traction motors are hardwired inparallel and/or series with at least three to five other motors.Although this arrangement allows for the motors to share a commonelectrical bus, it may be susceptible to large scale drive systemfailure. In these arrangements, a failure of one of the motors in thesame circuit may render all motors inoperable. For example, for motorsconnected in parallel, an electric failure that leads to a short circuitcondition in one of the motors may disable all of the other tractionmotors in the circuit. In such a case, if all of the traction motors forthe locomotive reside on the same circuit, the locomotive may lose alldriving capability. Thus, to prevent a situation in which the loss ofone motor disables the entire locomotive, a system for selectivelyisolating drive components that experience electrical failures may berequired.

One solution for maintaining the traction motor system functionality inthe event of a traction motor component failure is described in U.S.Pat. No. 6,497,182 B2 (“the '182 patent”). The '182 patent is directedto a system that purportedly incorporates a brake motor isolation switchdisposed in signal communication with at least one of the tractionmotors for electrically isolating a faulting motor from the othertraction motors.

The motor isolation solution provided by the system disclosed in the'182 patent is limited to traction motors in which the armature and thefield winding circuit of the motor are connected in series. As a result,any failure that results in tripping of the isolation switch effectivelyremoves both the armature and the corresponding field coil of the motorfrom the circuit. In certain situations, however, it may be advantageousto retain the ability to selectively remove only the failed component ofthe motor, rather than the entire motor. For example, in situationswhere a field winding of the motor has failed, it may be advantageous toallow the armature to remain in the circuit so that the dynamic brakingcapabilities of the armature are retained. While the '182 patent allowsfor a traction motor system to isolate a failed motor and to retain thefunctionality of the remaining motors, it may unnecessarily removeproperly functioning components from the system—components that mayotherwise contribute to the functionality of the drive system.

The presently disclosed traction motor drive system is directed toovercoming one or more of the problems set forth above and/or otherproblems in the art.

SUMMARY OF THE INVENTION

In accordance with one aspect, the present disclosure is directed to atraction motor drive system. The traction motor drive system may includea plurality of armatures arranged in parallel with one another. Thetraction motor drive system may also include a plurality of fieldcircuits arranged in series with one another, each field circuitassociated with a respective one of the armatures. The plurality offield circuits may be arranged in parallel with the plurality ofarmatures. The traction motor drive system may also include a fieldisolation system. The field isolation system may include a shunt circuitassociated with at least one of the field circuits. The shunt circuitmay have a first and second shunt terminal. The field isolation systemmay also include a first field switch arranged in series with theplurality of field circuits. The first field switch may be configured toswitch between the first shunt terminal of the shunt circuit and a firstfield terminal of at least one of the field circuits. The fieldisolation system may also include a second field switch, arranged inseries with the plurality of field circuits. The second field switch maybe configured to switch between the second shunt terminal of the shuntcircuit and a second field terminal of at least one of the fieldcircuits.

In accordance with another aspect, the present disclosure is directed toa method for selectively isolating fault conditions on a traction motordrive system. The method may include detecting a fault conditionassociated with at least one of a plurality of traction motors of thetraction motor drive system and identifying a field circuit from among aplurality of series-connected field circuits that corresponds to thetraction motor affected by the fault condition. The method may alsoinclude identifying a plurality of field switches for isolating thefield circuit from the remainder of the series-connected field circuits.The method may include generating a control signal for operating theidentified plurality of field switches. The control signal may beconfigured to cause a first field switch arranged in series with theplurality of series-connected field circuits to switch from a firstfield terminal of the identified field circuit to a first shunt terminalof a shunt circuit associated with the field circuit. The control signalmay also be configured to cause a second field switch arranged in serieswith the plurality of field circuits to switch from a second fieldterminal of the identified field circuit to a second shunt terminal ofthe shunt circuit.

According to another aspect, the present disclosure is directed to alocomotive. The locomotive may include a plurality of axles and aplurality of pairs of wheels, each pair of wheels attached to one of theaxles. The locomotive may also include a plurality of armatures arrangedin parallel with each other, each rotatably coupled to one of the axles.The locomotive may also include a plurality of field circuits arrangedin series with one another, each field circuit associated with arespective one of the armatures. The plurality of field circuits may bearranged in parallel with the plurality of armatures. The locomotive mayalso include a field isolation system. The field isolation system of thelocomotive may include a shunt circuit associated with at least one ofthe field circuits and comprising first and second shunt terminals. Thefield isolation system may also include a first field switch arranged inseries with the plurality of field circuits. The first field switch maybe configured to switch between the first shunt terminal of the shuntcircuit and a first field terminal of at least one of the fieldcircuits. The field isolation system may also include a second fieldswitch arranged in series with the plurality of field circuits. Thesecond field switch may be configured to switch between the second shuntterminal of the shunt circuit and the second field terminal of at leastone of the field circuits.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary locomotive that comprises a tractionmotor.

FIG. 2 provides a schematic of an exemplary traction motor drive systemincluding circuitry capable of isolating malfunctioning components.

FIG. 3 shows an orientation where each field winding can be individuallyisolated.

FIG. 4 shows an orientation where field windings are isolated in pairs.

FIG. 5 shows an orientation where field windings are isolated in groupsof three.

FIG. 6 provides a flowchart depicting an exemplary method for isolatingtraction motor components in the event of an electrical failure.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary locomotive 100 in which systems andmethods for traction motor isolation may be implemented consistent withthe disclosed embodiments. Locomotive 100 may be any electricallypowered rail vehicle employing DC traction motors for propulsion.Furthermore, any electrically powered vehicle employing DC tractionmotors for propulsion could also incorporate the systems and methods fortraction motor isolation consistent with the disclosed embodiments.According to the exemplary embodiment illustrated in FIG. 1, locomotive100 may include six pairs of wheels 101, with each pair of wheels 101attached to an axle 102 that is rotatably coupled to a traction motor103. Traction motors 103 may each include an armature 104 and a fieldcircuit 105. FIG. 2 illustrates the relationship between armature 104and field circuit 105 within a traction motor drive system 200.

Traction motor drive system 200 includes a plurality of mechanical andelectrical components that cooperate to propel locomotive 100. Tractionmotor drive system 200 may be divided into two distinct but cooperativesubsystems, a plurality of armature subsystems 201 and a field windingsubsystem 202. As shown in FIG. 2, traction motor drive system 200comprises a single field winding subsystem 202, which includes fieldcircuits 105 for each traction motor 103 of traction motor drive system200. Each traction motor 103 has a separate armature subsystem 201.

Field winding subsystem 202 may be connected in parallel with theplurality of armature subsystems 201. Within field winding subsystem202, each field circuit 105 may be connected in series with one another.In the exemplary embodiment, there are six armature subsystems 201, eachcorresponding to one of six traction motors 103. For clarity, FIG. 2shows only three of the six armature subsystems 201. Three additionalarmature subsystems 201 may be connected in parallel to armaturesubsystems 201 shown in FIG. 2. Of course, this embodiment may bealtered to accommodate a different number of traction motors 103 bychanging the number of armature subsystems 201 and the number of fieldcircuits 105 within field winding subsystem 202.

In addition to field circuits 105, field winding subsystem 202 may alsoinclude components necessary to operate field circuits 105 during normaloperation. For example, field winding subsystem 202 may also include achopper 203, a reverser 204, and a pair of field polarity switches 205,206. Chopper 203 may be serially connected to the plurality of fieldcircuits 105.

Chopper 203 may embody a power-regulation device configured to regulatecurrent through field circuits 105. By controlling the current throughfield circuits 105, chopper 203 may be configured to regulate the torqueof traction motors 103. By way of example, when locomotive 100 begins topull a load, it is the nature of traction motors 103 to require highamounts of current at low generator voltage to provide the torque neededto initially move locomotive 100 and its load. As locomotive 100accelerates, the requirement for current reduces while the appliedvoltage increases. Chopper 203 responds to this demand.

Traction motor drive system 200 may comprise field polarity switches205, 206 and reverser 204. By manipulating the direction of current flowthrough the field windings using field polarity switches 205, 206 andreverser 204, traction motor drive system 200 can control the directionof rotation of traction motors 103, allowing locomotive 100 to travel inboth the forward and reverse directions.

Reverser 204 is configured to act as a connection point to the series offield circuits 105. The pair of field polarity switches 205, 206 isconfigured to switch between the different connection points of reverser204. The first field polarity switch 205 may be connected to chopper 203and second field polarity switch 206 may be connected to a secondtraction bus 209. Field polarity switches 206, 207 may be configured tochange the polarity of field circuits 105.

Reverser 204 may be connected to the series of field circuits 105.Reverser 204 has four leads. The first pair of leads connects directlyto the series of field circuits 105. The second pair of leads is a setof connection points that field polarity switches 205, 206 can engage.When the directions of field polarity switches 205, 206 are switched,the switches connect to different leads of reverser 204, whicheffectively reconfigures field winding subsystem 202, reversing thedirection of the current flow through field winding subsystem 202 andits field circuits 105.

Field polarity switches 205, 206 of the exemplary embodiment aresingle-pole, double-throw switches. In a first position, field polarityswitches 205, 206 connect directly to the first pair of connectionpoints of reverser 204. In this mode, field polarity switches 205, 206allow current to flow directly through the series of field circuits 105.In a second position, field polarity switches 205, 206 connect to thesecond pair of connection points of reverser 204. In this mode, thecurrent must flow through reverser 204 before flowing through fieldcircuits 105 in the opposite direction that it flows when field polarityswitches 205, 206 are in the first position.

As shown in FIG. 2, each armature subsystem 201 may include armature104, a motor-brake switch 207, and other components necessary fordynamic braking, such as a grid resistor 210 and a dynamic brakingcontrol circuit 211. Armature subsystem 201 may include the componentsnecessary to operate armature 104 during both powering mode and brakingmode. Within each armature subsystem 201, armature 104 is connectedbetween first traction bus 208 and second traction bus 209. Duringnormal powering mode, motor-brake switch 207 may connect the second leadof armature 104 to second traction bus 209. The first lead of armature104 may connect to first traction bus 208 through the brakingcomponents.

Dynamic braking resistors, like grid resistors 210, are well known inthe art, and they are only used if the traction motor drive system 200is configured to perform rheostatic dynamic braking. Grid resistors 210may not be necessary to implement regenerative dynamic braking. Duringdynamic braking, traction motors 103 operate as generators when slowinglocomotive 100, generally by converting the kinetic energy of wheels 101into electrical energy. A plurality of grid resistors 210, each arrangedin series with one of the armatures 104, may be used to dissipate thegenerated electrical power as heat. Any method or device known in theart that is capable of dissipating or using the power generated bytraction motors 103 during braking can be used in place of gridresistors 210 and dynamic braking control circuit 211.

A brake switch 212 is used in conjunction with motor-brake switch 207 toswitch traction motor drive system 200 from powering mode into brakingmode. Traction motor drive system 200 may include a plurality of brakeswitches 212, each connected between one of armatures 104 and one ofgrid resistors 210. During the powering mode, brake switch 212 remainsopen, electrically isolating grid resistor 210. During the braking mode,brake switch 212 closes, providing an electrical connection betweentraction armature 104 and grid resistors 210 to allow grid resistors 210to dissipate the excess power produced during dynamic braking. Brakeswitch 212 can be any switch or contactor capable of performing thisfunction. In one exemplary embodiment, brake switch 212 is asingle-pole, double-throw switch. Brake switch 212 can be controlledmanually by an operator command, or it can change automatically whenmotor-brake switch 207 is moved into a brake position.

Traction motor drive system 200 may be capable of isolating at least onearmature subsystem 201 in which one or more components ismalfunctioning. Armature isolation may be realized by the selectiveoperation of a power switch 213 and motor-brake switch 207 connected toarmature 104. Each of the plurality of armatures 104 comprises a firstarmature terminal and a second armature terminal. The first armatureterminal is selectively coupled to a first traction bus 208 via powerswitch 213. The second armature terminal is coupled to motor-brakeswitch 207, which includes at least a first and second switch position.The first switch position may be configured to electrically couple thesecond armature terminal to second traction bus 209, and the secondswitch position may be configured to decouple the second armatureterminal from second traction bus 209.

Motor-brake switch 207 may be a single-pole, triple-throw switch that isable to isolate armature 104 from the remainder of traction motor drivesystem 200 in the event of an electrical failure affecting all or partof armature subsystem 201. According to an exemplary embodiment,motor-brake switch 207 may have at least three modes of operation: apowering mode, an isolation mode, and a braking mode. During thepowering mode, motor-brake switch 207 connects the second lead ofarmature 104 to second traction bus 209. To isolate armature subsystem201, motor-brake switch 207 shifts into a second mode that electricallydisconnects the second lead of armature 104 from any power source. This,in cooperation with the operation of power switch 213, electricallyisolates armature 104 from the remainder of traction motor drive system200. In the third position, motor-brake switch 207 may electricallycouple the second armature terminal to first traction bus 208 to shiftarmature 104 into braking mode.

In one embodiment, motor-brake switch 207 may be configured to isolatearmature 104 automatically in the event of an electrical failureaffecting all or part of armature subsystem 201. In another embodiment,motor-brake switch 207 may be configured to isolate armature 104 onlyafter receiving a command from an operator or another system oflocomotive 100 to isolate armature 104. There are a variety of otherswitches and contactors known in the art that are capable ofdisconnecting armature 104 that are equally suitable to operate asmotor-brake switch 207 of the traction motor drive system 200.Motor-brake switch 207 may include or embody any of these types ofcomponents.

Power switch 213 may be a single-pole, single-throw switch that is ableto isolate armature subsystem 201 from the remainder of the tractionmotor drive system 200 by disconnecting the armature subsystem 201 fromfirst traction bus 208. In one embodiment, power switch 213 may operateto isolate armature 104 automatically in the event of an electricalfailure affecting all or part of armature subsystem 201. Alternatively,power switch 213 could operate to isolate armature 104 only afterreceiving a command from an operator or another system of the locomotive100 to isolate armature 104. There are a variety of other switches andcontactors known in the art that are capable of disconnecting armature104 that are equally suitable for operating as power switch 213 oftraction motor drive system 200. Power switch 213 may include or embodyany of these types of components.

In the exemplary circuit of FIG. 2, motor-brake switch 207 and powerswitch 213 are configured to isolate armature subsystem 201, includingarmature 104, grid resistor 210, and dynamic braking control circuit211, from the remainder of traction motor drive system 200.Alternatively, motor-brake switch 207 could be a single-pole,double-throw switch capable only of switching between braking mode andpowering mode. In this configuration, to achieve armature isolation, adedicated isolation switch (not shown) could be incorporated to achievethe same result.

While not shown in FIG. 2, alternative configurations of traction motordrive system 200 may include fewer power switches 213 and motor-brakeswitches 207, such that each power switch 213 and motor-brake switch 207controls the current flow to multiple armature subsystems 201. It is notnecessary that each armature subsystem 201 have a devoted power switch213 and motor-brake switch 207. For example, pairs of armaturesubsystems 201 could share a common power switch 213 and a commonmotor-brake switch 207. Other configurations of armature isolationcomponents can be contemplated by one with ordinary skill in the art.

In addition to armature isolation, traction motor drive system 200 maybe configured to isolate defective or malfunctioning field circuits 105using a field isolation system 214 associated with field windingsubsystem 202. Field isolation system 214 comprises a shunt circuit 215,a first field switch 216, and a second field switch 217. Traction motordrive system 200 may include a plurality of field isolation systems 214,each field isolation system 214 associated with a respective one of thefield circuits 105. Also, the plurality of field isolation systems 214may be associated with a respective pair of field circuits 105. In FIG.2, traction motor drive system 200 contains three field isolationsystems 214, each corresponding with a pair of field circuits 105.

Within field winding subsystem 202, field circuits 105 are connected inseries with first field switch 216 and second field switch 217, whichcan remove a defective field circuit 105 from traction motor drivesystem 200. By shunting a defective field circuit 105, the remainingfield circuits 105 of traction motor drive system 200 continue toreceive power and operate normally. The embodiment illustrated in FIG. 2allows traction motor drive system 200 to achieve 4/6 of normal tractiveor braking effort despite a malfunctioning field circuit 105. When firstfield switch 216 and second field switch 217 engage to isolate a pair offield circuits 105, first field switch 216 connects to the first end ofshunt circuit 215, and second field switch 217 connects to the secondend of shunt circuit 215. In this configuration, field circuits 105 areshunted, such that the current continues to flow through the remainderof field winding subsystem 202.

Field switches 216, 217 can be any electromechanical component capableof isolating field circuit 105 from the remainder of traction motordrive system 200 in the event of an electrical failure affecting all orpart of field circuit 105. In one embodiment, field switches 216, 217may be single-pole, double-throw switches. There are a variety of otherswitches and contactors known in the art that are capable of isolatingfield circuit 105 from the remainder of traction motor drive system 200.Field switches 216, 217 may include or embody any of these types ofcomponents.

The operation of field switches 216, 217 may be automatic or manual. Inone embodiment, field switches 216, 217 could operate to shunt one ormore of the field circuits 105 automatically in the event of anelectrical failure affecting all or part of a malfunctioning fieldcircuit 105. Alternatively, field switches 216, 217 could operate toshunt field circuit 105 only after receiving a command from an operatorto isolate field circuit 105 from the remainder of traction motor drivesystem 200. In yet another embodiment, the operation of field switches216, 217 could result from a combination of automatic or manual inputs.For example, first field switch 216 may operate to shunt field circuit105 only after receiving a command to do so, and second field switch 217may operate automatically once first field switch 216 becomes engaged.

It should be emphasized that power switch 213 and motor-brake switch207, as well as first and second field switches 216, 217, can beseparately controlled such that isolation of armature subsystem 201 doesnot require isolation of field winding subsystem 202. Likewise,isolation of field winding subsystem 202 does not require isolation ofarmature subsystem 201.

The schematic in FIG. 2 shows exemplary traction motor drive system 200capable of isolating both armatures 104 and field circuits 105. It isalso contemplated, however, that traction motor drive system 200 may beimplemented with one of the isolation capabilities. For example,traction motor drive system 200 may include field circuit isolationcapabilities without necessarily requiring an armature isolation system.Alternatively, traction motor drive system 200 may be provided witharmature isolation capabilities and without the field isolationcapabilities. Thus, the system need not be limited to the specificembodiment of FIG. 2 but may have different configurations of thecomponents described.

It is contemplated that locomotive 100 may include additional componentsfor communication between an operator and traction motor drive system200. For example, a controller may be a processor capable of receivinginputs from sensors to detect electrical failures. The controller mayalso be configured to notify the operator of the occurrence of anelectrical fault and may allow the operator to send control signals toisolate the affected components. Locomotive 100 may include an operatorinterface that provides the operator a way to read fault notificationsand send commands to the controller. For example, the operator interfacemay include a processor for receiving notifications from the controllerand an output screen for displaying these notifications to the operator.The operator interface may also include an operator input system, like aseries of buttons, for the operator to send commands to the controllerto selectively isolate electrical components.

FIG. 2 shows a schematic for an exemplary traction motor drive system200 in which field circuits 105 are grouped in pairs. In the event of afailed field circuit 105, the pair of field circuits 105 that includesthe failed field circuit 105 will be shunted by connecting to shuntcircuit 215. In another embodiment, field circuit 105 could beindividually isolated by adding more field switches 216, 217 and shuntcircuits 215 to field winding subsystem 202 such that each field circuit105 would have two dedicated field switches 216, 217, as well as adedicated shunt circuit 215. In yet another embodiment, field circuits105 may be arranged into larger groups. Other embodiments andarrangements are possible and should be apparent to one skilled in theart.

FIGS. 3-5 show alternative configurations of field circuits 105. FIG. 3shows a configuration in which each field circuit 105 corresponds withits own field isolation system 214, so that each field circuit 105 canbe individually shunted. In this configuration, there will be two fieldswitches 216, 217 and one shunt circuit 215 for each traction motor 103.FIG. 4 shows a configuration of field circuits 105 in pairs, as shown inFIG. 2. In this configuration, every pair of field circuits 105 has acorresponding shunt circuit 215 and a pair of field switches 216, 217.Finally, FIG. 5 shows field circuits 105 arranged in groups of three. Inthe configuration shown in FIG. 5, each field isolation system 214 isassociated with a respective group of three of the field circuits 105.The configurations of field circuits 105 may be customized to suit theparticular needs of traction motor drive system 200. Furthermore,traction motor drive system 200 may organize field circuits 105 intogroups of varying sizes.

FIG. 6 provides a flowchart depicting an exemplary method forselectively isolating traction motor components in the event of anelectrical failure. The process commences when a sensor detects anelectrical fault condition associated with at least one traction motor103 of traction motor drive system 200 (Step 602). A sensor (not shown)capable of sensing an electrical change in a circuit may detect thefault condition. For example, a current sensor may detect a sudden surgein current within traction motor drive system 200 that corresponds withan electrical failure (or ground fault leakage current, etc.). Thesensor may communicate the electrical failure to a controller (notshown).

Once an electrical failure is detected, the location of the electricalfailure may be identified. In an exemplary process that detects anelectrical failure affecting field circuit 105, this may includeidentifying field circuit 105 from among a plurality of series-connectedfield circuits 105 that correspond to traction motor 103 affected by thefault condition (Step 604). In another embodiment, this may includeidentifying armature 104 from among a plurality of parallel-connectedarmatures 104 that corresponds to traction motor 103 affected by thefault condition. The same sensor that identifies an electrical fault mayalso be used to locate the electrical fault. For example, each armaturesubsystem 201 and each field circuit 105 may be associated with acurrent sensor to detect electrical faults. A controller may receive asignal from the sensor indicating the occurrence of the electricalfault. The controller may identify the location of the electrical faultbased on which sensor sent the signal.

To isolate the affected components, the controller may identify theswitches that correspond to the problematic electrical component (Step606). If the problematic component is field circuit 105, the controllermay identify the associated field switches 216, 217 for isolating fieldcircuit 105 from the remainder of the series-connected field circuits105. In one embodiment, the sensor may communicate the identity of fieldswitches 216, 217 to the controller when notifying the controller of anelectrical failure. Alternatively or additionally, if the problematicelectrical component is contained in armature subsystem 201, thecontroller may identify the associated motor-brake switch 207 and powerswitch 213 for isolating problematic armature subsystem 201 from theremainder of armature subsystems 201. Once the switches that are capableof isolating the affected electrical component are identified, thecontroller may initiate the component isolation.

To isolate affected field circuit 105, the controller may generate acontrol signal to operate field switches (Step 608). The control signalmay be configured to cause first field switch 216 arranged in serieswith the plurality of series-connected field circuits 105 to switch froma first field terminal of the affected field circuit 105 to a firstshunt terminal of a shunt circuit 215 associated with field circuit 105.The control signal may also be configured to cause second field switch217 arranged in series with the plurality of series-connected fieldcircuits 105 to switch from a second field terminal of the affectedfield circuit 105 to a second shunt terminal of shunt circuit 215associated with field circuit 105.

The controller may generate a second control signal to operatemotor-brake switch 207 associated with the identified affected armature104. The second control signal may be configured to isolate armature 104from traction motor drive system 200. Motor-brake switch 207 may be asingle-pole, triple-throw switch having three switch position settings:a powering mode, a braking mode, and an isolation mode. The secondcontrol signal may include a command to select the isolation positionsetting from among the three position settings of motor-brake switch207. To isolate affected armature subsystem 201, the process may alsoinclude generating a third control signal for operating power switch 213associated with the identified armature 104 to electrically disconnectthe identified armature 104 from power.

The third control signal may include a command to open power switch 213,which will disconnect armature subsystem 201 from first traction bus208. Upon receiving the third control signal, power switch 213 wouldopen, electrically disconnecting armature subsystem 201 from firsttraction bus 208. In this manner, power switch 213 and motor-brakeswitch 207 electrically isolate affected armature subsystem 210 fromtraction motor drive system 200, so that no current flows to affectedarmature 104. Power switch 213 may be a single-pole, double-throwswitch.

In one embodiment, the controller may generate a signal for notifying anoperator of the fault condition. The notification may provideinformation to the operator identifying the components affected by thefault condition. The controller may also receive a command signal fromthe operator requesting isolation of the fault circuit. In oneembodiment, the operator is also the locomotive operator.

INDUSTRIAL APPLICABILITY

The disclosed systems and methods for traction motor isolation describedherein provide a robust solution for enhancing the performance oftraction motor drive systems by allowing them to maintain maximumfunctionality in the event of an electrical failure affecting one ormore of its components. By isolating only portions of the affectedtraction motor, the traction motor drive system preserves thefunctionality of the remaining portions of the affected traction motorfor use in powering or braking. This has the additional benefit ofallowing dynamic braking even if some of the electrical components areinactive.

The presently disclosed traction motor drive system may have severaladvantages. Specifically, by limiting isolation to only those individualarmatures or field circuits that have failed, the presently disclosedisolation system may aid in maintaining maximum operational capabilitiesof the system. This is particularly advantageous when the locomotive isnot close to a repair station.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the disclosed systems andassociated methods for traction motor isolation of an electricallypowered rail vehicle. Other embodiments of the present disclosure willbe apparent to those skilled in the art from consideration of thespecification and practice of the present disclosure. It is intendedthat the specification and examples be considered as exemplary only,with a true scope of the present disclosure being indicated by thefollowing claims and their equivalents.

What is claimed is:
 1. A traction motor drive system, comprising: aplurality of armatures arranged in parallel with one another; aplurality of field circuits arranged in series with one another, eachfield circuit associated with a respective one of the armatures, whereinthe plurality of field circuits is arranged in parallel with theplurality of armatures; a field isolation system, comprising: a shuntcircuit associated with at least one of the field circuits andcomprising first and second shunt terminals; a first field switcharranged in series with the plurality of field circuits and configuredto switch between the first shunt terminal of the shunt circuit and afirst field terminal of the at least one of the field circuits; and asecond field switch arranged in series with the plurality of fieldcircuits and configured to switch between the second shunt terminal ofthe shunt circuit and a second field terminal of the at least one of thefield circuits.
 2. The traction motor drive system of claim 1, whereinthe first and second field switches are single-pole, double-throwswitches.
 3. The traction motor drive system of claim 1, furthercomprising a plurality of field isolation systems, each field isolationsystem associated with a respective one of the field circuits.
 4. Thetraction motor drive system of claim 1, further comprising a pluralityof field isolation systems, each field isolation system associated witha respective pair of the field circuits.
 5. The traction motor drivesystem of claim 1, further comprising a plurality of field isolationsystems, each field isolation system associated with a respective groupof three of the field circuits.
 6. The traction motor drive system ofclaim 1, wherein each of the plurality of armatures comprises a firstarmature terminal and a second armature terminal, the first armatureterminal selectively coupled to a first traction bus via a power switchand the second armature terminal coupled to a motor-brake switch, themotor-brake switch comprising at least first and second switchpositions, the first switch position configured to electrically couplethe second armature terminal to a second traction bus and the secondswitch position configured to decouple the second armature terminal fromthe second traction bus.
 7. The traction motor isolation system of claim6, wherein the motor-brake switch comprises a third switch positionconfigured to electrically couple the second armature terminal to thefirst traction bus.
 8. The traction motor isolation system of claim 7,wherein the motor-brake switch comprises a single-pole, triple-throwswitch.
 9. The traction motor isolation system of claim 6, wherein thepower switch comprises a single-pole, single-throw switch.